TAILORED STACKED HYBRIDS – AN OPTIMIZATION-BASED APPROACH IN MATERIAL DESIGN FOR FURTHER IMPROVEMENT IN LIGHTWEIGHT CAR BODY STRUCTURES

In latest body-in-white (BIW) concepts, engineers take into account a wider range of different materials to pursue a multi-material design approach. However, the lightweight potential of common materials like steel, aluminum or even fiber-reinforcement plastics (FRP) is limited. In keeping with the motto “the best material for the best application”, a new approach for a top-down material design is introduced. With the aim to develop an application tailored material, the multi-material concept is adapted for the thickness dimension of the component. Within this contribution a new optimization- based design methodology is applied on a stiffness relevant car body part. Starting with benchmark simulations of a reference BIW structure, a critical car body component is determined by an internal energy based method and a subsequent sensitivity analysis. The identified demonstrator component is later subdivided into multiple layers and submitted to a first optimization loop in which the developed methodology varies the material parameters for each single layer. Once an optimum for the through-thickness properties of the part is found, further optimization loops with concrete material pendants and manufacturing restrictions are carried out. The result is a hybrid laminate part consisting of steel and FRP plies. To achieve a further improvement in body characteristics and lightweight, the investigated part is redesigned by the aim of topology optimization. Finally, the tailored hybrid stacks are validated in BIW simulations and compared with the reference. The optimization-based approach allows a weight reduction up to 25 % while maintaining or even improving the BIW properties.